Shortly after the attack on the U.S. diplomatic compound in Benghazi last September, a phone call was placed from the area.

Whoever made the call was excited. "Mabruk, Mabruk!" he repeated, meaning "Congratulations" in Arabic.

Two sources with high-level access to Western intelligence services have told CNN the call was made to a senior figure in al-Qaida in the Islamic Maghreb, or AQIM. There is no proof that the call was specifically about the attack, in which U.S. Ambassador Chris Stevens and three other Americans were killed, but the sources say that is the assumption among those with knowledge of the call.

One of the sources says the phone call was discovered when a Western intelligence service trawled through intercepts of communications made in the wake of the attack. That source told CNN that the call was made specifically to Moktar Belmoktar, leader of an al-Qaida faction based in northern Mali.

CIA officials told CNN they had no comment on whether any call had been intercepted.

If the call was made and subsequently detected, it could fuel an already partisan debate in Washington over the Obama administration's initial public characterization of the Benghazi attack, and what information U.S. intelligence officials had about who was involved.

Critics say initial administration comments did not reflect the true intelligence about the incident, and were an attempt by the administration to avoid tying it to terrorism.

On Monday, Sens. John McCain, R-Ariz., Lindsey Graham, R-S.C., and Kelly Ayotte, R-N.H., issued a statement with more questions about the attack, saying:

"We do not know what person or persons, representing what executive branch agency or agencies, changed the unclassified talking points to remove references to Al-Qaeda and a terrorist attack in describing the attack on the U.S. Mission in Benghazi."

The administration says the unclassified talking points were the basis for comments made by the U.S. ambassador to the U.N., Susan Rice, on television talk shows in the immediate aftermath of the attack.

The senators added: "Al-Qaeda, its affiliated groups, and local militias were able to establish sanctuaries almost uncontested in the ungoverned spaces of eastern Libya. Some of these individuals were involved in the attack on the U.S. Mission in Benghazi."

Belmoktar's links to Libya

A veteran jihadist who had lost an eye while fighting in Afghanistan as a teenager, Belmoktar had established relationships with some of the more radical Libyan militia, and at the time of the Benghazi attack was putting together an elite unit specifically to attack Western interests in the Sahel and North Africa.

A few months later, that unit carried out the attack on the In Amenas natural gas facility in southern Algeria in which 33 foreign workers were killed. The group traveled through southern Libya on their way to the plant, according to counterterrorism officials.

Chadian officials say that Belmoktar himself is now dead, killed Saturday as French and Chadian special forces penetrated the remote Adrar des Ifoghas mountain range in northeastern Mali.

But French Defense Minister Jean-Yves Le Drian said Monday there was no confirmation that either Belmoktar or another senior figure in AQIM, Abou Zeid, had been killed during the French campaign against Islamist hideouts in northern Mali.

"I have no proof of the deaths of those two men," Le Drian said.

Nor is there proof that Belmoktar directed or was involved in the Benghazi attack. His group never claimed any responsibility for it.

But in the weeks after that attack on Sept. 11, several senior U.S. and Libyan officials suggested that members of al-Qaida in the Islamic Maghreb may have been involved, without offering details.

The president of Libya's parliament, Mohammed al-Magarief, asserted that U.S. intelligence had intercepted communications between elements of AQIM and Ansar al-Sharia, a group widely blamed for playing a part in the attack.